


Becoming Human

by Mega_purplezebracorn



Category: Undertale (Video Game)
Genre: F/M, Human AU undertale, Human Papyrus, Human Sans, This came to mind, but it’s cute I promise, humantale, i think it’s cute, idk - Freeform, kinda angsty, undertale - Freeform
Language: English
Status: In-Progress
Published: 2019-09-19
Updated: 2019-09-20
Packaged: 2020-10-21 16:55:35
Rating: Teen And Up Audiences
Warnings: Graphic Depictions Of Violence
Chapters: 5
Words: 3,534
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/20696891
Author URL: https://archiveofourown.org/users/Mega_purplezebracorn/pseuds/Mega_purplezebracorn
Summary: Sans discovers something about his past, and realised that problems he’d faced as a child can now be made right. Does he want to take the risk? How will everyone else react? What would Frisk think?





	1. Chapter 1

Frisk was at the skeleton brothers house, sitting in the kitchen. She had come over for movies and dinner, which she did more often these days (especially since Papyrus had gotten better at making spaghetti). 

Frisk liked hanging out with the guys and, since getting older, had gained a small crush on Sans. The shorter skeleton was easier to get along with, smart and funny. Frisk loved spending time with him the most. 

Speaking of the shorter skeleton, he was not here with her and Papyrus in the kitchen. In fact, she hadn’t seen him for a while. 

“Where’s Sans?” She asked the younger skeleton. Papyrus looked up, scanning the room and looking as though he too had just realised he wasn’t here. 

“HMM, WHY DON’T YOU GO FIND HIM HUMAN. HE CAN’T BE FAR?” Papyrus stated, turning back to his spaghetti sauce on the stove. 

Frisk thought about it, then decided why not and got off her chair to go look for the older skeleton. He wasn’t in the sitting room, or the bathroom? As she moved past the stairs she heard movement and muttering from the top floor. 

Frisk moved upstairs and along the hall. There, she found him in his room, fumbling with a reasonable stack of paper. Most of the sheets where crumpled and he was struggling to keep them all together.

Cocking her head, she alerted her presence by knocking on the opened door. Sans startled, turning to see Frisk. “oh, kid...whats up?” He asked, finally shuffling the papers into a neat enough pile before plopping them on his bed. They promptly separated stubbornly as soon as they weren’t in his hands. 

Frisk shrugged, looking past him and straight at the papers. “What’s that?” She asked, curious. She moved into the room to get a better look but Sans intercepted. 

“boring stuff.” He said, closing one eye and looking at Frisk nonchalantly. 

The young woman crossed her arms, determined. She saw Sans sag slightly. “ah...it’s honestly not that interesting. I-“

“Sans, just tell me.” Frisk smirked, shoving the skeletons shoulder. Frisk has grown a lot of over the years and, much to Sans disappointment, was slightly taller than him now at the age of 21. 

Sans laughed dryly. “geez kid...” he said, swiping a hand down his face in exasperation. Frisk didn’t budge, staring down at him with a smug grin. She was breaking him. “alright, it’s some journal extracts from my...Dad’s research.” He explained quietly, sitting on the bed and reaching for the papers.

That peaked Frisk’s interest. “You had a dad?” She asked thoughtlessly. 

Frisk heart clenched when she saw Sans stiffen, but then he laughed heartily. “‘course kid? why wouldn’t we? did you think me and Pap just...happened?” He grinned.

“I don’t know!” Frisk argues weakly, smiling despite herself.”it’s just surprising!” She says. Plopping down next to him on the bed, she gestured to the stack of papers again. “So what does it say?” 

Sans snorted. “nosy, aintcha?” He grinned when Frisk flushed and glanced away. He chuckled again. “it’s a long story, one I didn’t know about. I’m still going through it all. it’s...a bit of a mess...” he states, looking off in thought at the papers. Glancing at the papers, they were written in a really weird way? It looked like random symbols. Could Sans read this stuff?

Frisk is silent for a moment, watching Sans stare at the documents. 

Sans sighed suddenly, startling Frisk, before folding the papers and putting them on his bed again. He then gets up, placing a hand out for Frisk. “come on, dinner smells nearly ready.” Sans grins. Frisk eyes him and Sans laughs. “I’ll tell ya about it all when I’ve had a better look.” He said, nodding to the papers. 

She takes his hand and he raises her up, moving towards the door and only stopping to see if she was following him. Together they headed downstairs, those journal entries on Frisk’s mind all night.


	2. Chapter 2

A couple weeks after Frisk had found Sans with those papers, Frisk had almost forgot about them and the whole incident. She had other things on her mind, like her job at Grillby’s or her crush on Sans. You know, important stuff.

Tonight, she was heading over for another movie night. Toriel was busy tonight so Frisk and the skeleton brothers decided she could stay the night instead of being home alone. 

As she came up to the door, Papyrus came crashing out. “OH! FRISK!” He exclaimed, happy to see her but also looking terribly rushed. “I’M AFRAID I’LL HAVE TO LEAVE YOU AND SANS TO IT. I HAD ALREADY SPARED THIS TIME FOR UNDYNE AND ALMOST FORGOT! COULD YOU IMAGINE?! ME, THE GREAT PAPYRUS, FORGETTING ANYTHING?!” He guffawed. 

“ANYWHO, I HAVE LEFT SOME SPAGHETTI ON THE STOVE FOR YOU BOTH, THAT IS IF SANS COMES DOWN FROM HIS ROOM!” He seemed irritated and worried as he looking back into the house. He shook his head and gave Frisk one of his best smiles. “I’LL SEE YOU TOMORROW!” He exclaimed, finally rushing past her. And just like that he was gone.

Frisk shook her head in laughter, heading inside and closing the door behind her. “Sans?!” She called out through cupped hands. If he heard her, he didn’t say anything in response. 

Feeling hungry, Frisk went to the kitchen to fix a plate of spaghetti. Perhaps he will come down in a bit? Maybe he’s just busy? Frisk held in her snort; when was Sans busy with anything?

20 minutes passed with no sign or sound of Sans which wasn’t too abnormal, but after what Papyrus had said about Sans barely having left his room it was confusing. Frisk sighed and headed upstairs, expecting to shove Sans out of bed or something along those lines. 

Instead, Frisk opens the door abruptly to find the room is COVERED with paper; on the walls, floor, even the ceiling?! And in the centre of it, Sans sat at his desk, a whole chemistry set and beakers and bottles. Was that a microscope? What was happening here?!

“Sans?” Frisk tries softly. Sans makes a noise, like a grunt, in response. She takes it as a “come on in, don’t mind the mess!” sort of grunt, and steps up behind him. In front of him, journal and papers with those strange symbols are all over the table. Frisk stares in amazement as Sans begins to write notes in this ‘language’ as he scans a journal. 

Taking a look around at the papers around the walls she find they also have those strange symbols in them also. Some look old and quite neat, though it shifts to more aggressively written sheets that are messy and unkempt. Frisk wonders what they say.

“what’s up, kid?” Sans asks distractedly, head still bows over his desk. Frisk comes over to him and stands beside him, bending over his shoulder to take a peak. He writes quickly, his handwriting hardly distinguishable even if it was those symbols he was writing in the first place. It was almost soothing to watch.

Sans looks up then, face suddenly so close to hers. Frisk feels her face heat up uncomfortably so, just knowing she’s bright red. Sans also seems surprised by the close proximity as it sockets go wide. 

Frisk puts some space between them, suddenly sheepish. “Uuh, I just wanted...to see...” she gestured around her. “Also, Pap said you havent left your room all day.” 

She watches the skeleton digest this. Then he looks at the clock on the wall. “what...what day is it?” He asked. 

Well that was surprising.

“It’s Wednesday...?” Frisk told him, confused. 

Sans stared at the clock for a little longer before standing. Some papers that were hidden on his lap float to the floor, along with a pencil and an eraser. Sans looks at it then chuckles. “huh...there it is?” He says to himself, picking it up and putting it on his desk. 

Frisk feels intrusive all of a sudden, watching him pick up his papers. She bites her lip. “Uh...” she thinks of something to say. “Pap left some spaghetti on the stove? I’ve eaten but...”

She watches as sans straightens his spine, clicking it in some places. It’s weird and she winces since there’s nothing to soften the noise like her flesh would. 

“spaghetti sounds great!” He grins, placing a hand on the small of her back to lead her out. She gets one sparing glance at the bedroom-turned-study before the door is closed and she has to spend the rest of the evening wondering what those symbols say.


	3. Chapter 3

Frisk had looked into the symbols of course. She had scoured Toriel’s private library but, not finding anything there, moved onto the books that Alphys had at her home. She was a scientist after all, and Sans appeared to be looking at something science-y.

She came up empty handed though. Whatever it was that Sans was looking at, it wasn’t to the public’s knowledge yet. Maybe he didn’t want anyone to know, and that’s why he’d been so secretive about it all? Maybe it was dangerous stuff? Maybe someone would stop him if she told someone.

Frisk thought about asking Toriel or Alphys about the symbols but she trusted Sans. He didn’t seem the type to make something dangerous, especially at home with his precious brother there? 

Maybe she could confront him, demand an answer to what all this was? He’d said he’d tell her, but he hadn’t promised of course.

Conflicted, Frisk spent a week deciding what the best course of action was. She had thought many times of storming over there and demanding answers. Or maybe she could go for a more peaceful approach? 

Eventually, Frisk found herself going over anyway. She’s let it slip to Papyrus that she’d managed to get Sans out of his room the other day and since then he’d been trying to get her over to help him. She was his “secret weapon”, as he liked to put it. 

As she walked to the door, she heard Papyrus yelling. It wasn’t hard really, you could hear him yelling from a mile away from their house. The guy was naturally loud anyway. 

What caught her attention was that he was yelling Sans name.

Frisk knocked on the door. Then a lot louder when the yelling continued. Papyrus stopped yelling and there was a moment of silence until suddenly the door swung open and she was greeted with the smiling face of the younger skeleton. 

“FRISK!” He exclaimed happily, yanking her into the house. “THANK GOODNESS YOUR’E HERE! SANS IS UPSTAIRS AND I HAVEN’T BEEN ABLE TO GET HIM OUT AT ALL!” Papyrus snapped, glaring up the stares. 

“When was he last out?” Frisk asked, staring up the stairs too, as if Sans was just stood there.

Papyrus gave a long, slightly exaggerated sigh. “I THINK I HEARD HIM COME  
OUT LAST NIGHT? BUT I WAS HALF ASLEEP AT THE TIME.” Frisk nodded to show she was listening. “COULD YOU...WORK YOUR MAGIC, FRISK? I’M ALMOST CERTAIN THE WEDNESDAY YOU WERE HERE WAS THE LAST TIME HE ATE TOO?” 

Well that was worrying...and pressuring. What if she couldn’t get him out again? 

“Well last time I just opened the door and he came out? Did you not try that?” She asked, turning to look at the taller skeleton. 

Papyrus was staring at her with wonder. “I HAD TRIED BUT THE DOOR WAS HELD SHUT WITH HIS MAGIC? PERHAPS HE TRUSTS YOU MORE THAN I...?” There was sadness in his voice and Frisk felt her heart clench. 

“I-I’m sure that’s not the case Pap?” Frisk tried to reason. It didn’t make sense to her that Sans would lock Papyrus out but not her? But then maybe whatever this is was dangerous to monsters and not humans and Frisk was safe to come in but not Sans’ brother? That seemed plausible. “I-I’ll go talk to him?” Frisk said, squaring her shoulders. Worth a try, maybe she’ll finally get some answers. 

She reached Sans bedroom door relatively quickly, her body buzzing with nerves and curious energy. Frisk decided to knock first this time, but there was no answer so she turned the handle to find it unlocked. She cracked the door open and peaked inside. 

The room looked much the same as last time, though it was possible there were more papers out. Some papers had been changed around or taken down and now a white board also sat in the room. The board was covered in mathematics, with faded numbers beneath from where equations had been rubbed out. 

There was still no noise. At least, no sound from Sans, so Frisk opened the door wider. He was sat where she had last seen him: hunched over his desk. Though, now his desk was stacked and cluttered. Papers and books were everywhere, even on the floor? He was surrounded. 

“Sans-?” Frisk started but was interrupted.

“SANS?!!” Papyrus cried out, startling both the smaller skeleton and young woman, as he barged into Frisk. Sans turned sharply and Frisk nearly gasped. He looked tired. Or as tired as a skeleton could. 

“what are- what’s going on here?” Sans grumbled, standing from his chair in a wobbly fashion. 

“I suppose we could ask you the same thing...?” Frisk stayed, giving the room another look. It really was a mess. Where was his bed under all those books? “And when was the last time you’d slept?” Frisk asked pointedly. 

“what?!” Sans was glaring, probably more so from being interrupted. He had been deep in his notes after all. 

“BROTHER, WE HAVE BEEN WORRIED. I HAVE NOT SEEN YOU IN WEEKS!” Papyrus informed, stepping closer to his brother. Sans seemed to sag at that, all anger seeming to disappear. 

He was quiet for a moment before he shrugged and put on a smile. “sorry guys, I’ve been busy. I’m on a breakthrough of sorts.” He explained loosely.

Frisk felt her impatience grow. “And what exactly is this breakthrough?” She asked, crossing her arms.

“YES BROTHER, I HAVE TO AGREE. WHAT IS ALL THIS STUFF?” Papyrus asked, as if finally noticing he was surrounded by paper. 

Sans stared blankly, his eye lights gone. He was silent for a moment before sighing. Raising his hands in a shrug, he said “I guess it’s time I told you both.” He laughed.


	4. Chapter 4

“Told us what?” Asked Frisk, stepping forward and uncrossing her arms. Her impatience changed to concern. 

Sans chuckled mirthlessly, shaking his head. “I...found some stuff. Stuff that belonged to our dad Pap...” Sans started. 

Pap was instantly confused. “OUR DAD? WHAT DO YOU MEAN?” He continued to look around, looking for answers. “I DON’T UNDERSTAND? HE DISAPPEARED...?” Pap cocked his head at Sans.

“yeh, I know. And left absolutely nothing. Stupid fucker-“

“SANS?!” Pap gasped at the swear. Frisk would have laughed if the serious look on Sans face didn’t worry her so much. 

“well he was Pap! You don’t-!” Sans was yelling but stopped himself, taking a deep breath as he flexed his hands. When he looked back at them, his usually non-expressive smile was in place. “the point is, I found some stuff the guy left...interesting stuff. turns out he had a secret office in this house...” Sans paused.

Frisk frowned. “If it’s in the house, how did you not find it before?” 

Sans shrugged. “I wasn’t looking for it.” He grinned and Frisk rolled her eyes, sniggering. But then Sans shoulders drooped slightly. “I realised we had so much space between our rooms? it seemed weird. So, I shortcut to see what was there and found all these journals and files. tonnes of the stuff!” He explained, looking pensive. There was something important that he wasn’t alluding to, and that’s what worried Frisk more. She wondered if Pap had noticed too. 

“What was in the files?” Frisk asked, gesturing around her. 

Sans frowned then. He looked upset. Frisk wondered if he’d actually say. Years ago, when they had first met, Sans wouldn’t tell people anything. He was so secretive and it was quite a big flaw on his part. 

However, the past few years, he’d been opening up more. Pap has told Frisk it was probably because he didn’t have to worry about resets anymore, after he had come clean about them also. It was safe to say everyone was amazed he could remember every reset, but he wasn’t keen on talking about all of them. Frisk didn’t blame him. 

Sans sighed suddenly. “look, I know you guys want me to talk more but, this stuff is pretty...heavy? Pap, it involves our ma and yer birth and stuff. I am trying to be more open but it’s a struggle alright.”

Frisk was surprised; that was a lot of emotion for Sans to show just then. 

Papyrus sighed softly. “SANS, WE’RE NOT GOING TO PUSH YOU IF YOU DON’T WANT TO...IT’S JUST THAT WE WORRY ABOUT YOU, ESPECIALLY RECENTLY!” He said, coming over to his brother and resting his hands on sans shoulders as he crouched in front of him.

Frisk stepped over and took Sans hand, surprising him. Sans looked up at her wide eyed. “We just wanna know what’s going on and if we can help, idiot.” She smiled at him. 

Sans chuckled at that. “I guess I am being a bit of a bonehead.” He agreed. Frisk giggled while Papyrus groaned. 

“WELL BROTHER, IT CANT BE THAT BAD IF YOU’RE STILL ABLE TO TELL AWFUL JOKES.” Papyrus acknowledged, standing straight and putting his hands in his hips. He almost scowled but he was still concerned. 

Sans chuckled again. “nah it’s pretty messed up, I just haven’t made a joke in a while and it was all set up for me, bro.” Sans said cheekily. Frisk giggled again. 

The trio grew quiet again, as they remembered what they were supposed to be discussing, no one sure what to say. Sans sighed again. “so, I know Pap can’t read my dads writing. the old mans got his own kind of...language almost and I learnt it before ma passed.” Papyrus stiffened at that. “but these scribblings dad called writing state that me and Pap aren’t exactly what we’re supposed to be..?” Sans trailed off, looking pensive.

“What do you mean?” Frisk asked, still holding his hand. Papyrus nodded beside her, urging his brother to continue. 

“uuh..” Sans mumbled. He turned quickly, his hand falling from Frisk’s as he began looking for something on the desk. Frisk fought the feeling of being disappointed in favour of thinking it would be a miracle if he did find what he was looking for. It was ridiculously cluttered. 

“ah!” Sans gasped triumphantly, pulling a journal out that looked new apart from the scribbles that littered their pages. He flicked through. “so... I made some notes...” Sans stated, quickly finding his page and glaring at it as though it irritated him. 

“WHAT DOES IT SAY BROTHER?” Papyrus asked, leaning over. No point really, Frisk could clearly see it was written in the strange symbols from before. 

Sans is silent for a moment, grimacing in thought. Frisk could almost see the cogs turning in his brain. “ah it’s tricky...” Sans said , glancing at his brother and dear friend. “I knew one day I’d probably have to tell you but it doesn’t make it easier I guess...” Sans laughed. 

“STOP WASTING TIME BROTHER, I WANT TO KNOW. ALL THIS HESITATION IS MAKING FRISK AND I NERVOUS!” Papyrus nagged, gesturing to Frisk during his rant. Sans glanced at her and Frisk felt her heart clench. Sans looked sacred. “HONESTLY BROTHER, WHAT IS THE POINT IN STALLING IF YOU BELIEVE IT TO BE INEVITABLE-“

“we’re half human...”


	5. Chapter 5

**Summary for the Chapter:**

> Dis be a short one...

There was a lengthy pause. Papyrus was frozen, digesting the information while Frisk stared open mouthed at Sans. Meanwhile, the shorter skeleton’s eye lights had gone and he looked terrified. 

Frisk was the first to move. She took Sans hand again and brought the other to his jaw, lifting his head so he was facing Papyrus and herself. “You’re half human?” She repeated, wanting clarification. 

Sans nodded slowly, his eye lights finally returning. 

“WHAT DOES THIS MEAN BROTHER?!” Came Papyrus’ voice, shrilly and sudden, causing Frisk to startle. 

“Pap, it means what it means? You’re half human?” Frisk said, frowning. 

“YES, BUT-“ 

“ma was a human Pap. I...I don’t know much about how they met, heh...but I do know that they must of loved each other, as corny as that sounds...” Sans was babbling. It was kinda sweet, but he looked so sad. 

“SANS?” Papyrus whispered. Frisk and Sans looked over to see that the younger skeleton almost seemed small. He was curled in on himself. 

Frisk looked back over to see Sans was crying. Without thinking, Frisk reached over and wiped his single tear away. Sans flinched.

“Let’s watch a movie.” Frisk suggested. This conversation was getting too somber, and seeing Sans cry struck something in her. She could always ask another time. 

“good idea kid...” Sans agreed. This was getting far too somber.


End file.
